A combination of computational modeling and experimental techniques was used to study metal-porphyrin complexes containing in crude oil (petroporphyrins). The TDDFT method was applied to calculate the electronic absorption spectra of vanadyl and nickel petroporphyrin complexes. A correlation was established between the ligand structure and the characteristics of B- and Q-absorption bands. The permanent electric dipole moments of the petroporphyrin complexes were shown to differ from each other by a factor of six. The simulated spectrum of the vanadyl-porphyrin mixture was found to closely match the experimental spectrum of the sample solution isolated from the asphaltene fraction of crude oil, enabling prediction of the electronic absorption spectra of mixtures with a known ligand composition. The sublimation of the petroporphyrin mixture under high vacuum conditions was experimentally investigated by two methods: evaporation from a Knudsen cell with in-situ mass spectrometric detection and sublimation from a quartz crucible with ex-situ recording of the sublimate absorption spectra. In both cases, the composition of the vapor above the analyzed petroporphyrin mixture depended on the process time and temperature. This result opens up new opportunities for separating petroleum porphyrin mixtures into their individual components and producing thin films with controlled properties.

The possibility of separation of petroleum vanadyl porphyrins from asphaltene clusters on the silica gel adsorbent whose mean pore diameter (27 & Aring;) exceeds the size of petroporphyrin molecules but not of asphaltene clusters has been studied. For this purpose, the time- and concentration-dependent adsorption of heavy oil asphaltenes and vanadyl porphyrins contained in them was studied by a UV-vis spectroscopic method in order to identify differences in the mechanism and rate of their adsorption. It has been established that at initial asphaltene concentrations above the critical nanoaggregate concentration (CNAC) and critical clustering concentration (CCC), the shape of the kinetic adsorption curves is significantly influenced by nonaggregated asphaltene molecules still remaining in solution. The rate of attainment of adsorption equilibrium is limited by the rate of adsorption of asphaltene nanoaggregates. The rate of adsorption of free vanadyl porphyrins is up to 2 orders of magnitude greater than the adsorption rate of nanoaggregates, which indicates independent diffusion of these two types of components inside the adsorbent pores. Asphaltene clusters do not make a significant contribution to the total adsorption due to the size-exclusion effect. Using experimental data on time-course and equilibrium adsorption, we revealed the impact of kinetic and concentration factors on the efficacy of vanadyl porphyrin isolation. Due to the size-exclusion effect toward asphaltene clusters, a 6-fold enrichment of the adsorbate with petroporphyrins is achieved. The results of the study can lay the basis for more effective approaches for petroporphyrin isolation.

Benzene proved to be a more effective eluent compared to chlorinated organic solvents traditionally used for chromatographic recovery of vanadyl petroporphyrins from the dimethylformamide (DMF) extract of asphaltenes on a column packed with mesoporous silica gel. Low eluting power of benzene can be compensated by moistening of the silica gel adsorbent. An increase in the silica gel moisture content from 0 to 7.7% does not lead to a decrease in the efficiency of the separation of vanadyl porphyrins from nonporphyrin components but leads to a tenfold decrease in the eluent consumption. A decrease in the eluent flow rate from 0.8 to 0.12 mL min –1 (per gram of the adsorbent) leads to a 1.5-fold increase in the yield of vanadyl porphyrins of required purity. An increase in the adsorbate : adsorbent weight ratio from 1 : 833 to 1 : 83 does not lead to a decrease in the efficiency of the vanadyl porphyrin recovery. Elution with benzene under optimum conditions (adsorbent moisture content, eluent flow rate, adsorbate : adsorbent ratio) allows the recovery of 3 times larger amount of petroleum vanadyl porphyrins from the DMF extract of asphaltenes than when using chloroform and dried silica gel under equal other conditions.

An approach to the preparation of porphysomes by the noncovalent immobilization of petroleum porphyrins in the liposome membranes was developed for the first time. Modified nanocontainers with different compositions were prepared in terms of this approach. A composition with doxorubicin optimal in the physicochemical and encapsulation parameters was tested on the M-HeLa cervical cancer cell line and healthy Chang Liver cell line to evaluate the anticancer potential. In order to control the release of the drug substance, remote destruction of the porphysomes was carried out by laser irradiation at 405 nm wavelength. Statistically significant changes in dynamic light scattering data confirming liposome decomposition were obtained for the compositions with 2 and 10 mol.% petroleum porphyrins.

The composition of purified vanadyl porphyrins recovered from the resins of heavy oils possessing high and low vanadium contents was investigated. Vanadium content in the resins of the heavy oils under study differs by a factor of ca. 15. To recover and purify vanadyl porphyrins from the resins, extraction by N,N–dimethylformamide (DMF) with subsequent two-stage column chromatography on silica gel and sulfocationite were employed. The change of structural-group composition and content of vanadyl porphyrins in the products obtained at each stage was evaluated using Fourier IR and UV-Vis spectroscopy. Analysis of the purified vanadyl porphyrins using MALDI mass spectrometry determined distribution of their most abundant types (etio- and DPEP) and identified C27–C39 homologs for the resins possessing high vanadium content and C28–C39 homologs for the resins with low vanadium content.

High-vanadium heavy oil asphaltenes were fractionated by a sequential precipitation method. Using FT-IR spectroscopy, elemental analysis, and optical spectroscopy, the differences in the compositions of the asphaltene fractions were thoroughly investigated. To isolate and purify vanadyl porphyrins (VPs) from the asphaltenes, extraction with N,N-dimethylformamide (DMF) followed by two-step column chromatography on silica gel and sulfocationite was employed. The effects of VPs on the solubility of the asphaltene fractions were evaluated based on optical density variations in the solvent/precipitant system in a kinetic mode. It was found that, in most cases, adding petroleum VPs to toluene solutions of asphaltene fractions decreases the solubility of these fractions. The highest effect of VPs on the solubility of the asphaltene fractions was observed for samples with a high concentration of polar heteroatom groups and low aromaticity.

An adsorption-extrographic method was developed for preconcentration of petroleum vanadyl porphyrins from the dimethylformamide (DMF) extract of high-vanadium-content heavy petroleum asphaltenes. The procedure consists in preliminary adsorption of components present in the benzene solution of the DMF extract onto coarsely porous silica gel under the conditions of increased selectivity of the adsorbent to vanadyl porphyrins, followed by their elution from silica gel with chloroform. The development of the procedure is based on the results of a spectroscopy study of the adsorption of asphaltenes and vanadyl porphyrins present in the DMF extract of asphaltenes onto coarsely porous silica gel. The kinetics of the adsorption of asphaltenes and vanadyl porphyrins is described most adequately by a pseudo-second-order equation; both adsorbates are characterized by comparable rates of the attainment of the adsorption equilibrium. The equilibrium adsorption isotherms of asphaltenes and vanadyl porphyrins formally correspond to the Brunauer–Emmett–Teller multilayer adsorption model. The ability of silica gel for more selective adsorption of vanadyl porphyrins increases with a decrease in the initial concentration of the initial DMF extract of asphaltenes. The suggested adsorption-extrographic method allows preparation of a concentrate with ~20% higher content of vanadyl porphyrins having higher spectral purity, compared to the preconcentration by traditional preparative chromatography.

In the present work, the first data on the adsorption behavior of petroleum vanadyl porphyrins in the presence and absence of asphaltenes are afforded. As adsorptives, N,N' - dimethylformamide extract of asphaltenes containing 9.88 wt % vanadyl porphyrins and high-purity vanadyl porphyrins preisolated from the extract by the sulfocationite-based chromatographic method were used. As adsorbents, two mesoporous silica gels distinguished in their ability to slow down the rate of diffusion of asphaltene nanoaggregates were chosen. Changes in adsorptive concentration upon adsorbing were monitored spectrophotometrically. Time- and concentration-dependent adsorption studies have been conducted, and particular features in the adsorption behavior of asphaltenes and vanadyl porphyrins have been revealed and used in modeling the intermolecular asphaltene-vanadyl porphyrin interactions occurring inside the adsorbent pores. An adsorption kinetic experiment showed that the asphaltenes diffuse inside the adsorbent pores in the aggregated form and reduce the diffusion rate of vanadyl porphyrins virtually up to the rate of the asphaltene nanoaggregates themselves. An equilibrium adsorption experiment revealed that when a Langmuir-type adsorption happens the asphaltene nanoaggregates adsorbed are composed of 5-8 monomers, which is well consistent with the Yen-Mullins model. No competition for free adsorption sites between asphaltenes and vanadyl porphyrins was observed, which indicates a coaggregation mechanism of vanadyl porphyrin uptake. This assumption was supported by an adsorption thermodynamic study displaying that enthalpy change of adsorption obtained by the van't Hoff method takes positive values for both the asphaltenes and vanadyl porphyrins present in them (Delta H degrees > 0) but not for isolated vanadyl porphyrins (Delta H degrees < 0). An average molecular weight of asphaltene monomers required for thermodynamic calculations was derived from their matrix-assisted laser desorption/ionization (MALDI) mass spectrum mathematically simulated using a log-normal distribution function. The results of the present work contribute to better understanding the nature of asphaltene-petroporphyrin interactions responsible for aggregation and adsorption properties of these petroleum components.

The prospects of using asphaltenet and resind of industrial vacuum oil residue as a feedstock for the production of pure vanadyl porphyrins are shown. Vanadyl porphyrins are separated from petroleum objects via extraction with DMFA with subsequent purification by column chromatography on silica gel and sulfonic cation exchanger. The composition of resulting vanadyl porphyrins is studied using matrix-assisted laser desorption/ionization mass spectrometry (MALDI) and high-performance liquid chromatography (HPLC). The metalloporphyrins obtained in this way can be used as bases for the creation of catalysts for different chemical processes as an alternative to their synthetic production.

Specific features of the distribution of vanadium and nickel during fractionation of heavy oil resins were examined using the example of heavy sulfurous oils from the Permian and Carboniferous deposits of the Volga-Urals oil and gas basin (Russian Federation). Fractionation of the resins was performed by silica gel column chromatography, followed by extraction with dimethylformamide (DMF). It was found that, during fractionation by adsorption chromatographic separation and extraction, vanadium and nickel compounds in the resins were predominantly distributed into the components with reduced content of carbonyl and carboxy groups, as well as of aliphatic structures.

In the present work, the first data on the catalytic activity of d-metal complexes of petroleum porphyrins obtained via two-stage re-metallization (acid demetallization with subsequent metalation) of high-purity petroleum vanadyl porphyrins are presented. During acid demetallization of petroleum vanadyl porphyrins, the highest yield (49%) and spectral purity of free petroporphyrin bases were achieved with concentrated sulfuric acid and a diluted solution of vanadyl porphyrins in chloroform. In the series of divalent cations of Mn, Fe, Co, Ni, Cu, and Zn, only the last four metals are complexed with demetallated petroporphyrins without significant changes in their component composition, whereas the interaction with Mn and Fe cations causes an evident structural transformation or even full degradation of petroporphyrin macrocycles, respectively. The composition and spectral purity of petroleum porphyrin-containing reactants and products were analyzed by FT-IR, UV-Vis, NMR, and MALDI-TOF mass spectroscopic methods. The obtained petroporphyrin-based d-metal complexes were assayed by the reaction of 2-mercaptoethanol oxidative dimerization, in which the copper porphyrins exhibited the highest catalytic activity.

The byproduct of ethylene tar has a high content of mono-, bi-, and polycyclic aromatic compounds, as well as cycloalkenes, including aromatic cycloalkenes. This paper evaluates the prospects of using ethylene tar as an additive in the visbreaking process of vacuum residue. A series of experiments on visbreaking of vacuum residue with additives of various refinery streams and ethylene tar were performed in a laboratory flow reactor. As a result of a comparative study of the composition of vacuum residue visbreaking products by different methods, it was shown that the use of ethylene tar compared with kerosene, light cycle oil, and heavy cycle oil allows an increased yield of the target product with a higher proportion of aromatic hydrocarbons. A comparative analysis of the characteristics of asphaltenes and resins of visbreaking products indicates a general trend of changes in the process of visbreaking vacuum residue with refinery streams and ethylene tar. A comparison of the colloidal instability index showed that the use of ethylene tar allows attainment of a more stable visbreaking product concerning refinery streams as additives.

The review discusses currently relevant methods for studying petroleum resins. A significant proportion of the research work deals with the study of resins in heavy oils, for which experimental approaches have been systematized and the possibilities and limitations of the mass spectrometric, spectroscopic, X-ray, and chromatographic methods have been discussed. Published data on the effect of resins on the stability of asphaltenes in heavy oils and other petroleum stocks has been analyzed. In addition to experimental approaches, an important factor for understanding the role of resins in the aggregation of asphaltenes is studying their intermolecular interactions using quantum-mechanical calculations. Commonly known approaches to the concentration, fractionation, and purification of heteroatomic petroleum components from heavy oil resins using extraction and chromatographic methods for the isolation of chemical compounds from complex multicomponent mixtures have also been considered.

Asphaltenes and resins from petroleum vacuum residue were shown to be the promising raw materials for obtaining pure vanadyl porphyrins. Vanadyl porphyrins are recovered from petroleum objects via the extraction of dimethyl formamide (DMFA) followed by purification on a chromatographic column using silica gel and sulfocationite. The composition of the obtained vanadyl porphyrins was studied by means of mass spectrometry with matrix assisted laser desorption/ionization (MALDI) and high performance liquid chromatography (HPLC). Thus obtained metalloporphyrins can be used as a basis to create catalysts for various chemical processes, which may serve as an alternative to their synthesis.

The development of efficient methods for preconcentration and purification of petroleum metal porphyrins is the necessary condition for further progress of basic and especially applied research concerning the properties of these compounds and their role in oil genesis and maturation. This study deals with chromatographic preparation of high-purity vanadyl porphyrins using a sulfuric acid cation exchanger that can be readily prepared from silica gel and sulfuric acid and is simple in use. At the silica gel : sulfuric acid : water weight ratio of 60 : 15 : 25, the suggested sulfuric acid cation exchanger retains most efficiently nonporphyrin impurities of the asphaltene polar extract, whereas a significant fraction of vanadyl porphyrins (up to ~50%) passes through the chromatographic column virtually without retention with the stationary phase. In contrast to traditional adsorbents, the suggested sulfuric acid cation exchanger allows preparation of spectrally pure vanadyl porphyrins in one chromatographic purification step, thus ensuring the minimal consumption of the eluent and adsorbent. High purity of the vanadyl porphyrins obtained was confirmed by mass-spectrometric and spectroscopic methods of analysis.

Changes in the composition and properties of heavy oil during thermolysis in the temperature range of 250-410 degrees C in the presence of molten sodium without hydrogen has been studied. Addition of sodium results in the decrease in the sulfur content in the products of thermolysis by the factor of 1.5 at 250 degrees C and a more than two-fold decrease at 350 degrees C and higher. A decrease in the sulfur content without sodium is recorded only during thermolysis at 350 degrees C and is less than 10%. Viscosity and density of the products of thermolysis with and without sodium almost do not differ and correspond to nearly 90 mm(2)/s at 20 degrees C and API gravity is higher than 26, respectively. Effect of sodium on the quantitative distribution of components (hydrocarbons, resins, and asphaltenes) in the products of thermolysis and distillate fractions i.b.p.-350 degrees C is insignificant. The amount of vanadium and nickel weakly depends on the presence of sodium in the process of thermolysis of heavy oil. Addition of sodium results in the growth of insoluble particles in the products of thermolysis.

The presented review considers the currently relevant methods for studying petroleum porphyrins. For this purpose, the experimental approaches used during the investigation of the structure, concentration, and properties of metal complexes of petroleum porphyrins and their free bases are systematized, and the capabilities and limitations of the used methods (mass spectrometric, spectroscopic (electron paramagnetic resonance, UV–visible electronic absorption spectroscopy, and X-ray techniques) as well as high-performance and gel penetration liquid chromatography) are discussed. Published approaches to the concentration, fractionation, and purification of petroleum porphyrins based on the extraction and chromatographic methods of recovery of chemical compounds from complex multicomponent mixtures are also analyzed.

The practical potential of petroleum porphyrins still remains underestimated because of the absence of satisfactory simple and effective methods for their isolation in pure form. Our work aims to provide a solution for this problem via use of sulfuric acid loaded macroporous silica as an unprecedentedly effective adsorbent for deep petroporphyrin purification. Using chromatographic columns of reduced volume (4 cm3), a series of experiments on optimization of chromatographic conditions for silica-based sulfocationite were carried out. As a source of petroleum porphyrins, the primary concentrates of vanadyl porphyrins isolated on silica gel column from DMF extracts of heavy oil asphaltenes have been used. UV-vis and MALDI-TOF mass-spectrometric methods were employed for vanadyl porphyrin analysis and identification. We established that in a narrow range of water and acid content equal to [Formula: see text]25 and [Formula: see text]15 wt.%, respectively, silica-based sulfocationite becomes able to retain a bulk of polar petroleum components with exception of porphyrins, which thus leave the column first. A preparative-scale purification of vanadyl porphyrins by the sulfocationite-based method was performed for the first time and 18.5 mg of excellently pure product were obtained. Considering the extremely simple preparation and excellent purification performance of our novel sulfocationite, it could greatly facilitate access to high-purity petroleum porphyrins.